148 Double allowances: transitional provisions.U.K.
(1)No allowance shall be made under or by virtue of any of the provisions of Part I in respect of, or of premises including, or of expenditure on, a building or structure if, for the same or any other chargeable period, an allowance is or can be made under any of the provisions of Part II, IV or V in respect of, or of expenditure on, that building or structure.
(2)No initial allowance under Part I shall be made in respect of expenditure on the provision of an asset if that expenditure is expenditure in respect of which a deduction may be allowed under section 137; and no allowance under Part IV shall be made in respect of any expenditure if it is expenditure in respect of which such a deduction may be allowed.
(3)Where a deduction is allowed for any chargeable period under section 137 or 138 in respect of expenditure represented wholly or partly by any assets, there shall not be made or allowed—
(a)any writing-down allowance under Part I, or
(b)except under Part VII, any allowance or deduction in respect of wear and tear, obsolescence or depreciation of those assets,
for any chargeable period during any part of which they are used by the person carrying on a trade for scientific research related to that trade.
(4)No allowance shall be made by virtue of section 134 in respect of any expenditure if for the same or any other chargeable period an allowance is or can be made in respect of it under any of the provisions of Parts I and II.
(5)No allowance shall be made under Part II in respect of, or of the expenditure on, any machinery or plant if, for the same or any other chargeable period, an allowance is or can be made in respect of that expenditure under the provisions of section 122.
(6)Expenditure in respect of which a deduction may be allowed under section 137 shall be disregarded for all the purposes of Part II; and where a deduction in respect of any expenditure has been allowed under that section in taxing a trade carried on by any person, section 81 shall not apply on that person’s bringing into use for the purposes of the trade any machinery or plant representing that expenditure.
(7)This section shall not have effect in relation to any chargeable period ... ending after 26th July 1989.